Introduction
Cosmetic expiration information is intended to help consumers judge when a product is likely to remain stable and safe to use, but the information can be difficult to interpret or even locate. The U.S. Food and Drug Administration (FDA) states that ordinary cosmetics are not required by U.S. law or regulation to carry a specific shelf life or expiration date. Also, products regulated as drugs, including products that are both drugs and cosmetics, must meet drug stability and expiration dating requirements (U.S. Food and Drug Administration [FDA], n.d.). This distinction matters for consumer research because items commonly grouped together as “beauty products” may have different legal classifications. Sunscreens, acne treatments, and cosmetics with certain drug claims can fall under drug or cosmetic drug requirements even when consumers perceive them as cosmetics.
Expiration information also has a practical safety function. Cosmetic products can change with time because preservatives degrade, microorganisms can be introduced through repeated use, and exposure to heat, moisture, air, or light can affect product stability (FDA, n.d.). Empirical work on mascara has found microbial contamination in used products and has documented consumer use of makeup beyond labeled expiration periods (Giacomel et al., 2013). These findings do not mean that every product becomes unsafe immediately after a printed date, but they establish that product age, storage, and contamination can matter. A label therefore has value only if consumers can find it and understand what it means.
One common labeling format is the Period After Opening (PAO) symbol, which typically displays a number of months that a cosmetic is expected to remain usable after opening. Campanella and Costanza (2011) describe PAO as a way of communicating product stability after opening while also noting the absence of a single standardized scientific protocol for determining PAO across all cosmetic types. From a user experience perspective, PAO adds a memory requirement: the consumer must know or estimate when the product was first opened and then calculate the relevant end point. In interviews with cosmetic users and industry employees in the United Kingdom and China, Wang et al. (2025) similarly found that consumers may ignore expiry guidance because several perceived risks compete with one another. Financial and social considerations can sometimes outweigh physical or performance concerns, and difficulty remembering when a product was opened can reduce the usefulness of PAO information.
Research from other product categories provides adjacent evidence that label format and visibility can influence valuation. In a study of 6,255 medication users, Pons et al. (2019) found substantial difficulty reading and understanding medication labels, while larger type and highlighted expiration information were among the most accepted improvements. In food labeling, Sapci and Sapci (2020) used an experimental auction to compare “sell by” and “expires on” labels and found that the more explicit expiration wording was associated with higher willingness to pay. Medication and food labels operate under different regulatory and behavioral conditions from cosmetics, so these studies cannot establish how cosmetic users will respond. However, they still support the broader proposition that reducing ambiguity by improving visual prominence can affect how consumers process shelf life information.
Expiration awareness also intersects with sustainability, but it requires caution. Cosmetic waste can contribute to packaging and chemical waste streams, and improved consumer knowledge has been proposed as one element of broader waste reduction strategies (Daughton, 2003; Liu, 2025). The study didn’t measure disposal volume, wastewater contamination, packaging waste, or ecological outcomes. Therefore, its environmental relevance is indirect: if clearer expiration information helps consumers avoid forgotten products, unnecessary replacement, or disposal of largely unused items, reduced waste is a plausible downstream possibility rather than a measured effect.
The resulting gap is behavioral and design-focused. Existing work identifies safety concerns, consumer risk perceptions, and labeling difficulties, but there is limited direct evidence on whether a simple increase in expiration label visibility is associated with changes in day-to-day cosmetic product use. The present study therefore examined: To what extent is a prominent calendar-date expiration label associated with changes in short term product use and self-reported future purchasing intentions? The study was designed as an exploratory pilot rather than a causal test. It was expected that a more visible date would be associated with greater expiration awareness and, for at least some participants, a change in product use patterns or future purchasing intentions. Importantly, the desired outcome was not simply “more consumption.” A more expiration-aware response could include increasing use to avoid waste, maintaining an appropriate recommended routine, reducing use when an expiration date is farther away than expected, avoiding unnecessary repurchases, or discarding a product when continued use is not appropriate.
Materials & Methods
This study used an exploratory, single-group pre/post quasi-experimental design with a six-day self-reported journaling period. Twenty adults aged 18 or older completed the study. Recruitment occurred through Instagram story post and direct outreach to adults known to the researcher, creating a convenience sample. Participants were not randomly selected or randomly assigned, and no separate control group was included. Each participant therefore provided their own pre-intervention and post-intervention observations. This design reduces some between-person variability but does not isolate the sticker intervention from time effects, study participation effects, or other uncontrolled influences.
The Google Form began with informed consent information describing the study purpose, procedures, risks, confidentiality, voluntary participation, and safety reminders. Participants were instructed to stop using a product if irritation, redness, or discomfort occurred. The study materials specified that participants should choose one topically applied skincare, makeup, or body care product that they owned, used at least weekly but not daily, and believed to be within approximately two years of expiration while still having more than two weeks of expected usable time. In practice, the selected products were heterogeneous and included skincare, body-care, sunscreen, and at least one makeup product. Because U.S. regulatory classification depends on intended use and claims, some selected items, such as sunscreen or SPF containing products, may be regulated as drugs or cosmetic-drug combinations rather than solely as cosmetics. The study did not independently classify each product under FDA law; “cosmetic product” is used in this article as a consumer facing category unless regulatory status is specifically discussed.
During Days 1–3, participants recorded their usual product use without intentionally changing their behavior. For each day they selected an amount-per-use category: Not at all, Small, Moderate, or Large and a frequency category: Not at all, Once, Twice, or More than twice. The survey also recorded baseline awareness of how close the product was to expiration on a 1–10 scale and asked participants to describe the visibility of the existing expiration display.
On Day 4, participants were instructed to write a full calendar-date expiration date on a sticker, tape, or paper label and place it where the information would be more visible on the product container. They submitted a photograph of the labeled product and reported the placement location. Participants whose products used a PAO symbol were instructed to approximate the opening date by looking back to the purchase date and then convert the PAO period into a calendar date. This procedure created an important source of measurement uncertainty because purchase date and opening date are not necessarily the same. Six participants entered an explicit PAO period such as 12 months in the expiration information field. One additional participant reported that no expiration date was present, meaning an accurate intervention date could not be established for that product. All 20 completed cases were retained in the analysis to avoid selective post hoc exclusion, but these intervention date uncertainties are treated as limitations.
During Days 4–6, participants repeated the same daily amount and frequency journaling. They then answered open-ended questions about how their use changed, whether companies should change expiration label design, what design elements should be improved, how greater expiration awareness might affect future purchases, and, when applicable, whether they preferred a written calendar date or the original PAO display.
The primary quantitative outcome was an exploratory Consumption Index created for this study. Frequency was coded 0 = Not at all, 1 = Once, 2 = Twice, and 3 = More than twice. Amount was coded 0 = Not at all, 1 = Small, 2 = Moderate, and 3 = Large. For each participant-day, the index was calculated as Frequency × Amount. Multiplication was chosen because a day with zero reported use should produce a zero use score, while increases in either frequency or amount should increase the joint use index. However, both components are ordinal. A score of 3 does not establish three times the physical amount or frequency represented by a score of 1, and multiplying the values does not create a validated ratio-scale measure of product volume. The measure is therefore referred to as an exploratory composite index rather than as direct consumption volume.
For each participant, the three daily index values from Days 1–3 were averaged to create a pre-intervention mean and the three values from Days 4–6 were averaged to create a post-intervention mean. Participant-level change was calculated as post minus pre. Group means and standard deviations were then calculated from these 20 participant level period means. Because the sample was small and the outcome was derived from ordinal ratings, the primary inferential analysis used a two-sided Wilcoxon signed-rank test rather than relying on a paired samples t test. Zero change scores were omitted from the signed rank calculation using the conventional Wilcoxon approach. Rank-biserial correlation was calculated as a nonparametric effect-size estimate. A nonparametric percentile bootstrap with 10,000 paired resamples was used to estimate a 95% confidence interval for the mean paired change.
A sensitivity analysis examined the frequency and amount components separately rather than assuming that their product was the only meaningful representation of use. For each participant, pre- and post-intervention mean frequency ratings and mean amount ratings were calculated from the three daily entries and tested with separate Wilcoxon signed rank tests. The amount analysis should be interpreted especially cautiously because several participants entered a nonzero “amount per use” response on days when frequency was recorded as zero, indicating some ambiguity in how that survey item was understood. The composite index is less affected by that inconsistency because a zero frequency mathematically yields zero daily use.
Qualitative responses were analyzed using single researcher, inductive thematic coding. The researcher first read all open-ended responses in full, identified recurring ideas without imposing a predetermined code list, and retained the most frequently recurring ideas as candidate themes. Operational definitions were then written for the retained themes. A response could receive more than one code when multiple ideas were explicitly present. Each respondent-by-theme combination was recorded in a binary matrix, with 1 indicating that the theme was present and 0 indicating that it was not. Ambiguous statements were not assigned a theme unless the relevant idea was explicit. Frequencies were calculated by summing each theme column. Because all coding was performed by one researcher, no inter-rater reliability statistic was available; this is reported as a limitation rather than treated as evidence of coding reliability.
Results
Baseline expiration awareness was low. On the 1–10 awareness item, the mean was 2.85 (SD = 2.37), the median was 2.0, and 10 of 20 participants selected 1, indicating that they had essentially no awareness of how close the selected product was to expiration. Existing labels also presented visibility problems. 13 participants (65%) reported at least one negative visibility feature: 10 said the indication was hard to find because it was on the bottom, six said it was too small, and one said the expiration indication did not exist on the product. Because participants could select multiple visibility descriptions, these category counts overlap.
Table 1 presents participant-level mean daily Consumption Index values. Reanalysis of the original daily entries produced a pre-intervention mean of 2.13 rather than the previously reported 1.85, and a post-intervention mean of 3.10 rather than 2.65. The resulting relative change in the exploratory index was 45.3%. Eleven participants increased, six had no change, and three decreased. Thus, the raw daily data show a heterogeneous response pattern rather than a statistically demonstrated two-pattern distribution response.
The mean paired increase in the Consumption Index was 0.97 points. The 95% bootstrap confidence interval for the mean change was 0.42 to 1.52. The Wilcoxon signed-rank test indicated a pre/post difference, W = 9.0, p = .006, with a rank-biserial correlation of .83. These statistics describe association within this single-group pre/post sample; they do not establish that the sticker alone caused the change.
The sensitivity analysis showed that frequency changed more clearly than amount. Mean frequency increased from 1.18 (SD = 0.64) to 1.52 (SD = 0.63), with a mean paired increase of 0.33 and a 95% bootstrap confidence interval of 0.13 to 0.55. The Wilcoxon test was W = 1.0, p = .011, with a rank-biserial correlation of .96. Mean amount rating increased from 1.62 (SD = 0.63) to 1.85 (SD = 0.62), but its mean paired change of 0.23 had a 95% bootstrap confidence interval spanning zero (-0.02 to 0.48), and the Wilcoxon test was not statistically significant, W = 20.0, p = .133. The post-intervention increase in the composite index therefore appears to have been driven more consistently by changes in reported frequency than by changes in the ordinal amount category.
The open-ended responses helped characterize why participants responded differently. The most frequent explicit theme was time urgency or deadline pressure (n = 8): these participants described using the product more because they wanted to finish it before expiration or felt pressure from seeing the date. Visual prompting or reminder effects were explicit in five responses, including statements that the sticker “reminded” the participant to use the product or helped integrate it into a routine. Four responses emphasized that the expiration date was far away or uncertain, reducing the reason to increase use; this group included the participant whose product had no expiration date. Three responses explicitly described routine or safe-use constraints, such as using the product only after showering or avoiding excessive application because of skin concerns. Three responses explicitly mentioned monetary value or avoiding waste. These codes were not mutually exclusive.
The response patterns also included potentially appropriate decreases or nonincreases. One participant reported reducing the amount after learning that the product expired later than expected, explaining that the product did not need to be used as quickly. Another participant maintained a recommended routine because using more products could be undesirable for the skin. These responses were retained as valid expiration-aware management behaviors rather than classified as intervention failures.
Future purchasing was measured only as intention. 18 of 20 participants provided a clear statement that greater expiration awareness would affect how they intended to shop for products. Common intentions included choosing products with longer remaining shelf life, buying fewer overlapping products, considering whether a product could realistically be finished before expiration, and delaying repurchase until an existing product was used. One response was incomplete and one discussed future usage rate rather than a purchasing decision, so neither was counted as evidence of a future purchasing intention. No subsequent purchases were observed.
Participants also reported specific label design preferences. When asked what should be improved, 14 of 20 selected size (70%), 13 selected location (65%), six selected color (30%), two selected symbols (10%), and three selected “Nothing” (15%). The options were multiple-select. Separately, 16 participants (80%) said in their written response that current company expiration label designs should be changed, while four did not support a general change or considered their existing label adequate. Thirteen participants (65%) placed the intervention sticker on the front or main body of the container, three placed it on the top or lid, two on the bottom, one on the side, and one on the back.
PAO preference required additional data cleaning. Six participants entered an explicit PAO period in the expiration information field. Of those six, four answered the optional PAO preference question. All four considered a written date useful: three preferred the written date format, while one preferred displaying both a written date and PAO information. Three participants whose expiration entries were not explicit PAO periods also answered the optional question; those responses were excluded from the PAO preference count because the item instructed non-PAO users not to answer. The revised analysis therefore does not claim that 100% of all PAO participants preferred replacing PAO with a calendar date.
Discussion
The results provide preliminary evidence that making expiration information more visible was associated with a short term change in reported cosmetic product use in this small convenience sample. The corrected participant level analysis is stronger than the original descriptive percentage alone: the exploratory Consumption Index increased from 2.13 to 3.10, the paired Wilcoxon test was statistically significant, and the rank-biserial effect-size estimate was large within this sample. At the same time, the study design doesn’t justify a causal statement. There was no randomized control condition, the observation period was only six days, and all use was self reported. The most defensible conclusion is therefore that a visible calendar-date intervention was followed by and associated with an observable behavioral signal that warrants more controlled investigation.
The sensitivity analysis narrows the interpretation of that signal. Frequency ratings increased significantly, whereas amount ratings considered separately did not. This matters because the Consumption Index is researcher-created and unvalidated. Multiplying two ordinal scales is useful as an exploratory way to combine use dimensions, but it can’t be interpreted as literal product volume, and the 45.3% relative increase shouldn’t be translated into a claim that participants physically consumed 45.3% more cosmetic product. The separate-component results suggest a more specific pattern: after the sticker was added, participants more consistently reported using the selected product on more occasions, while the amount used per occasion changed less consistently. Future studies could improve measurement by weighing containers, using pump counts, tracking standardized application units, or collecting device-assisted usage data.
The qualitative responses further show why “more use” should not be treated as the universal goal. A high visibility expiration label may support expiration-aware product management in several directions. Some participants increased use because the date created urgency or made a forgotten item more noticeable. Others maintained a stable routine because additional application was unnecessary or potentially undesirable. One participant reduced use after discovering that the product would remain usable longer than expected. These responses demonstrate that a person can respond to better information without increasing consumption. In particular, the participant who avoided excessive application for dermatological reasons shouldn’t be described as resistant to the intervention; the response may represent appropriate risk-aware decision making.
This nuanced interpretation is consistent with Wang et al. (2025), who found that cosmetic expiry behavior reflects multiple perceived risks rather than a simple awareness deficit. Financial concerns can encourage consumers to continue using a product, physical concerns can discourage use, and routine can shape whether new information changes behavior. The present study adds a small design intervention signal to that literature: when expiration information was made more salient, some participants altered their behavior, but the direction and magnitude depended on the context of the product and the user. The result therefore supports investigating label visibility as one component of risk communication rather than as a complete solution.
The findings from adjacent medication and food studies should also be interpreted at the appropriate level. Pons et al. (2019) showed that medication users frequently experience label readability problems and strongly support highlighting expiration information. Sapci and Sapci (2020) showed that explicit food expiration language can affect willingness to pay. Neither study establishes that a cosmetic calendar-date sticker will produce the same behavioral effect, because the products, regulations, risks, and purchasing contexts differ. Their relevance is theoretical: they demonstrate that consumers respond to information architecture and labeling clarity in other domains. The present pilot contributes preliminary direct evidence in a cosmetic/personal care context, but replication is needed before the pattern can be generalized.
The future purchasing result also requires conservative wording. Eighteen participants described intentions to shop differently after becoming more aware of expiration dates, including checking shelf life, reducing duplicate purchases, or waiting longer before replacement. These are self-reported future purchasing intentions, not observed purchasing behavior. Intentions can fail to translate into action, especially once the immediate study context is removed. A longitudinal followup using receipts, purchase logs, retailer data, or repeated surveys would be necessary to determine whether the intervention changes actual acquisition patterns.
The PAO conversion procedure is one of the study’s most consequential methodological limitations because the intervention depended on the accuracy of the date displayed. PAO begins when a product is opened, not when it is purchased. If a participant bought a product weeks or months before opening it, using purchase timing as a proxy could shift the displayed date substantially. That error could either exaggerate or reduce perceived urgency. The issue is not merely a minor measurement inconvenience; it directly affects the independent variable manipulation. Future studies should recruit only participants who know the actual opening date, ask participants to begin a standardized product at enrollment, or separately test PAO comprehension without converting PAO to a calendar date.
The regulatory implications should likewise remain narrow. FDA states that ordinary cosmetics are not federally required to bear a specific shelf life or expiration date, but drugs and cosmetic-drug products are subject to different stability and expiration requirements (FDA, n.d.). Since this study included consumer products that may fall into more than one regulatory category, it cannot support a single universal legal recommendation. The findings support a design question that manufacturers and regulators could test further: whether more standardized expiration information improves consumer decision making. Any proposal for mandatory calendar-date labeling would require larger studies across product categories, stability profiles, packaging types, and regulatory classifications.
Environmental implications are plausible but were not measured. The study didn’t quantify product disposal, packaging waste, chemical release, or ecological harm. It therefore cannot claim that the sticker prevented bioaccumulation or directly reduced environmental pollution. The more limited inference is that expiration-aware product management could potentially reduce avoidable product waste if consumers buy fewer redundant items, use suitable products before they are discarded, and replace products more strategically. The pathway is consistent with broader discussions of cosmetic and personal care waste (Daughton, 2003; Liu, 2025), but it remains a hypothesis for future research.
Several additional limitations should be addressed before further interpretation. First, n = 20 is small and the participants were recruited through convenience methods, limiting demographic and geographic representativeness. Demographic variables were not collected in the supplied dataset, so subgroup differences by age, gender, skin type, income, or culture can’t be evaluated. Second, the six-day observation period is too short to determine whether behavior persists. Third, self-report journaling can introduce social desirability and demand-characteristic bias. The Hawthorne effect may be especially relevant because participants knew that their behavior was being studied; the three-day baseline does not eliminate that possibility. Fourth, participants selected different products with different prices, recommended applications, package designs, and original expiration displays. Fifth, the exploratory Consumption Index assumes numerical structure in ordinal categories that has not been validated. Sixth, qualitative coding was performed by one researcher, so inter-rater reliability wasn’t assessed. Finally, one participant lacked an identifiable expiration date and several PAO conversions depended on uncertain opening dates.
A stronger follow-up study would use a larger sample, random assignment to visible label and control conditions, standardized or stratified product categories, a longer observation period, and objective usage measures. A factorial design could separately manipulate font size, contrast, placement, symbol type, and calendar-date wording to determine which visual elements matter most. Researchers could also test whether an intervention changes safe disposal, actual repurchasing, or product stockpiling over several months. Because the current data suggest that frequency changed more consistently than amount, future measurement should distinguish “how often” from “how much” rather than collapsing them into a single primary outcome.
In conclusion, this exploratory pilot doesn’t prove that expiration labels cause consumers to use more amount or that manufacturers should universally adopt one format. It does show that a simple high visibility calendar-date intervention was associated with a measurable short-term shift in reported use frequency and with widespread self-reported intentions to manage future purchases more deliberately. The most important contribution is therefore not a claim of regulatory proof, but evidence that expiration label visibility is a testable design variable with a behavioral signal strong enough to justify larger controlled research.
Conflicts of Interest Statement
The author declares no conflicts of interest.